Earthquakes and wind storms have caused significant damage to mobile homes and similar structures. One reason for such damage is that typical supports do not dampen the vertical displacement of the mobile home. A strong earthquake or windstorm is thereby free to violently jolt the mobile home, displacing furniture and injuring occupants on the inside.
Mobile homes are also vulnerable to earthquakes and windstorms because many supports do not prevent the mobile home from shifting horizontally in relationship to the ground. Thus, an earthquake is likely to tear the mobile home horizontally away from sun porches, cabanas, and utility connections. Indeed, typical support systems do not prevent the mobile home from shifting off the supports entirely, which can severely damage or destroy the mobile home. Additionally, typical supports do nothing to prevent a heavy wind load from overturning the mobile home, or to prevent a wind load from ripping the roof free, as can so easily occur during a tornado.
One type of such typical supports is illustrated in U.S. Pat. Nos. 4,261,149, and 4,546,581 (Gustafson). These patents disclose a plurality of individual supports that attach to the mobile home frame and are interconnected by strut stabilizing rods. The supports rest atop wooden blocks or other support surfaces, but are not normally attached thereto. In an earthquake, the support system and the mobile home move as a single, rigidly interconnected unit.
As can be readily seen, this support system normally offers nothing other than friction between the supports and the wooden blocks or other surfaces to prevent horizontal shifting during an earthquake or a wind storm. An earthquake can even shake the supports off of the wooden blocks or other supports, causing the mobile home to tumble. Furthermore, a heavywind load on one side of the mobile home can cause the mobile home to flip. Likewise, this type of support does nothing to prevent a region of low pressure from tearing the roof off of the mobile home.
U.S. Pat. No. 4,125,975 (Soble) discloses a support system that attempts to limit horizontal displacement and to provide some resistance to an overturning wind load. This support system includes several telescoping stanchions that are rigidly attached to the mobile home frame. An equivalent number of casings are provided to receive the telescoping stanchions. These casings may be embedded in the ground and surrounded by concrete or may be above the ground and bolted to a concrete foundation. The casings prevent the coach from shifting horizontally during an earthquake, and offer some resistance to overturning from a wind load.
However, there are several shortcomings to this type of support system. First, it appears that the entire weight of the mobile home rests on bolts which pass through holes in the stanchions and which rest atop the upper lips of the casings. Because bolts are structurally weak, the undamped vibration of an earthquake can cause the bolts to shear, thereby allowing the telescoping stanchions to crash down on the bottom of the casings with the weight of the mobile home. The casings could then be destroyed and the concrete broken, requiring expensive replacement or repair.
Second, this support system does nothing to dampen vertical motion and instead allows the telescoping stanchions to move freely in the vertical direction. Thus, an earthquake could cause substantial damage to the interior of a mobile home by overturning furniture, and could cause occupants to fall. Additionally, this system does nothing to filter minor vibrations that come from smaller earthquakes or other sources, which can nevertheless cause alarm or annoyance to occupants.
Third, this type of support system offers only limited resistance to wind forces. A strong wind may uplift and flip a mobile home by merely overcoming its weight and the friction between the stanchions and the casings. Similarly, with no restraint against vertical movement, one set of supports on one side of the mobile home could come loose and permit tipping over and secure damage to the mobile home. Additionally, this support system does nothing to protect the roof from tearing off in a hurricane or tornado.